1. Field of Invention
This invention relates to an improved unmanned aerial vehicle system.
2. Discussion of Prior Art
Military forces have come to rely on Unmanned Aerial Vehicles (UAV's) to conduct reconnaissance and surveillance missions when those missions may endanger a flight crew and their aircraft.
Many aircraft types have been adapted for unmanned operation including fixed-wing, rotary-wing and lighter-than-air. Rotary-wing aircraft have proven unsatisfactory because of their high rate of energy consumption which limits range and payload capacity. They also have inherently high levels of vibration which causes problems for sensor payloads.
Lighter-than-air craft have been used as UAV's, largely as tethered surveillance aircraft. As they tend to be vulnerable targets and are slow to take up position, lighter-than-air UAV's have had very limited use.
Nearly all UAV's that have been operationally deployed are of the fixed-wing planform and are essentially large model airplanes with more robust construction. For example, AAI Corporation's “Pioneer™” (a trademark for unmanned aerial vehicles for AAI Corporation with a website aaicorp.com) was the first UAV to be fielded by the U.S. military (1986) and the same airframe configuration is still in use. Although tremendous advances have been made in UAV payloads (sensors, cameras, communication systems, etc.), and avionics (guidance and navigation); the aircraft for delivering these payloads have remained substantially unchanged for nearly twenty years.
Many UAV's designed on the fixed-wing planform have become so expensive they have begun to defeat one of their basic design functions: protecting expensive aircraft. This problem has become so pervasive that the more costly UAV's have been modified to carry so-called “parasite” UAV's. Parasite UAV's are small, inexpensive parafoil UAV's; such as those invented by Glen BAiley, STARA Technologies, Inc. (U.S. Pat. No. 6,758,442; filed Oct. 30, 2002 issued Jul. 6, 2004). Bailey's invention allows an expensive system such as “Pioneer™” to stay in a safe standoff position while the parasite UAV's are released to fly the last leg of a dangerous mission. The parasite UAV's are electronically controlled and directed to their targets.
Using a very expensive UAV to position an inexpensive one is not a satisfactory solution to cost problems. At least two inventions have been proposed as more affordable methods of utilizing parasite UAV's. One invention uses a mortar to loft the small parafoil UAV's to altitude. The other utilizes an artillery gun to launch the parafoil UAV's (vectorsite.net). Both these systems have common deficiencies. Both systems are only as accessible as the nearest mortar or howitzer. Additionally, howitzers and mortars require highly trained crews to operate them, just like the systems they propose to replace. They, too, need to be called in; just like the fixed-wing systems. Both systems also suffer because they induce tremendous G-forces on their payloads: as much as 17,000 G's for the artillery gun and 7,000 G's for the mortar. These ultra-high G-forces create engineering, construction and materials problems.
Still another invention called “SkyLite™” by an Israeli (a trademark of the company Raphael for unmanned aerial vehicles) company, Raphael, mentioned at vectorsite.net attempts to resolve the unresponsiveness problem of fixed-wing UAV's. This invention has a UAV with wings that close like scissors over the back of the fuselage. This allows the UAV to be launched from a tube mounted on a vehicle or carried and launched by a person. This is a complex invention with the concomitant considerations about durability and reliability. The complexity of this invention with the resultant high cost leave it at a competitive disadvantage. This is particularly true for non-military markets where “real-world” costs are often the single most important consideration. The “SkyLite” (a trademark of the company Raphael for unmanned aerial vehicles) is ejected from its launch tube and flies to altitude using an electric motor and pusher propeller, taking a significant time to reach altitude. Like its fixed-wing cousins, this invention cannot “place” sensors (or other paylods) on the ground or on a rooftop for example. It can only land where its specialized retrieval equipment is located.
In another attempt to solve the problem of slow response associated with the presently deployed UAV systems, Miniature Air Vehicles (MAV's) have been developed. MAV's are highly engineered and micro-miniaturized aircraft such as the invention of Woodland (U.S. Pat. No. 6,056,237; issued May 2, 2000). MAV's have not proven to be satisfactory as yet due to cost issues, reliability issues and durability issues. The over-riding problem with MAV's is their inability to carry useful sized payloads. The payload capacities of these systems range from a few grants to a few hectograms.
The Disadvantages of Present UAV Systems:
(a) They require delivery and setup time. They must be called-in, unpacked and assembled. This dramatically reduces their responsiveness.
(b) They require dedicated crews of three or four at the low end to as many as twenty or more to operate the large, sophisticated “Predator™” (a trademark of General Atomics Aeronautical Systems, Inc. for unmanned aerial vehicles) built by General Atomics Aeronautical Systems, Inc.
(c) Their operators require a high degree of specialized training to use each specific UAV system.
(d) The cost of these systems range from a high of $20 million for the aforementioned “Predator™” (a trademark of General Atomics Aeronautical Systems, Inc. for unmanned aerial vehicles) to a low of $250,000 for the “Raven™” (a trademark of AeroVironment, Inc. for unmanned aerial vehicles) built by AeroVironment, Inc. (Kerstein, “Boston Herald, May 11, 2005). These systems are expensive.
(e) In an attempt to make UAV's more readily available and quicker to deploy, they have been scaled down. For example, the aforementioned “Raven™” (a trademark of AeroVironment, Inc. for unmanned aerial vehicles) has a wingspan of only 4.5 feet. This small size, however, creates serious disadvantages. Small airfoils mean small payloads and shorter ranges.
(f) Fixed-wing UAV's take a lot of time getting to an operational altitude and can take considerable time going to their intended targets. Small fixed-wing UAV's are particularly slow, flying at only 20-60 mph. Large, powerful motors and the extra energy used by high speed flight are too heavy for small UAV's.
(g) When not in use, today's UAV's are burdensome at best and truly logistically problematic for the larger models. The smallest UAV widely deployed by U.S. forces to date takes three large backpacks to store and transport.
(h) Presently deployed UAV's cannot independently place sensors where they cannot land and they can land only in locations where there are specialized retrieval systems. Without these retrieval systems the UAV's essentially crash land.